The motors carried a payload of gold nanoparticles, and researcher found that almost three times more particles reached the stomach lining when carried by the motors, compared to swallowing them alone.

In the experiment, mice ingested tiny drops of solution containing hundreds of micromotors.

They became active as soon as they hit the stomach acid, zooming toward the stomach lining at a speed of 60 micrometres per second.

The engineers estimate the motors can self-propel for up to 10 minutes.

The burst of propulsion helped the cone-shaped motors penetrate and stick in the mucous layer covering the stomach wall.

“It's the motor that can punch into this viscous layer and stay there, which is an advantage over more passive delivery systems,” explained Zhang.

Buoyed by its success, the University of California team is now working on similar nanomachines for applications including drug delivery, diagnostics, nanosurgery and biopsies of hard-to-reach tumours.